1. Field of the Invention
This invention relates generally to computer and communication networks, and more specifically, to handling of encrypted data in a deployable communication system used to provide secure voice, video and data services to multiple remote users.
2. Background of Related Art
In 1970, the Secure Telephone Unit (STU-I) was developed, followed in 1975 by the STU-II, and finally in 1987 by the third generation STU-III.
The STU-III terminals are designed to operate as either an ordinary telephone or a secure instrument over a dial-up public switched telephone network (PSTN). The STU-III operates in full-duplex over a single telephone circuit using echo canceling modem technology. Typically, STU-IIIs come equipped with 2.4 and 4.8 kbps code-excited linear prediction (CELP) secure voice. Secure data can be transmitted at speeds of 2.4, 4.8 and 9.6 kbps, though data throughput between two STU-IIIs is only as great as the slowest STU-III.
A STU-III operates by taking an audio signal and digitizing it into a serial data stream, which is then mixed with a keying stream of data created by an internal ciphering algorithm. This mixed data is then passed through a COder-DECoder (CODEC) to convert it back to audio so it can be passed over the phone line. STU-IIIs also allow a serial data stream to pass through the phone and into the ciphering engine to allow its usage as an encrypted modem when not used for voice.
The keying stream is a polymorphic regenerating mathematic algorithm which takes an initialization key and mathematically morphs it into a bit stream pattern. The keying stream is created by the key generator, and is the heart of the STU-III. A portion of the keying stream is then mixed back into the original key, and the process is repeated. The result is a pseudo-random bit stream that if properly implemented is extremely difficult to decrypt. Even the most sophisticated cryptographic algorithm can be easily expressed in the form of a simple equation in Boolean algebra, with the initialization keys being used to define the initial key generator settings, and to provide morphing back to the equation.
While STU-III provides secure communications, audio quality was vastly improved with the development of purely digital Standard Telephone Equipment (STE) devices.
An STE device utilizes an ISDN digital telephone line connection. There is substantial improvement in voice quality using an STE as opposed to the STU-III used over analog telephone lines. Most STE devices are STU-III secure mode compatible with enhanced abilities including voice-recognition quality secure voice communication, and high-speed secure data transfers (up to 38.4 kbps for asynchronous or 128 kbps for synchronous data transfers). When connected to an analog telephone line, an STE unit will only support STU-III voice and data capabilities.
The STU-III and STE are quite useful in fixed use, i.e., in an office environment or perhaps carried to another location having access to analog or digital telephone line access. However, deployable, remote communications are also desirable.
FIG. 7 is a depiction of a conventional deployable secure communication system.
In particular, as shown in FIG. 7, a secure encryption STE 700 with suitable interface hardware is utilized to provide a connection path to a wireless connection to a similarly secure STE via a satellite antenna 914. In the conventional system of FIG. 7, an ISDN link is utilized between the STE 700 and a suitable satellite two-way communication transceiver and antenna 914.
In operation, voice data is encrypted by the STE 700, and transmitted in a secure environment over a physically secure satellite, e.g., an M4 INMARSAT satellite terminal 914.
It is vitally important that the STE 700 stay physically secured, to maximize protection of the information being passed thereover. Also, to further maximize protection of the information, the satellite terminal 914 is conventionally set up and maintained within a secure environment, and travels with the STE 700.
Conventional systems are typically physically large, e.g., the size of a van. More importantly, such conventional systems require all elements to be maintained in a secure environment, including the data transport system (e.g., satellite communication system) over which the data travels to another secure communications terminal. Such secure data transport systems are costly to install and maintain, and always run a risk of being compromised.
There is a need for a small, lightweight, easily portable and easily deployable communication system that is not only even more secure than conventional systems, but which also allows flexibility in use of non-secure data transport systems.